Starboard Module Reference: event.h

Defines the event system that wraps the Starboard main loop and entry point.

The Starboard Application Lifecycle

               * ----------
               |           |
             Start         |
               |           |
               V           |
         [===========]     |
    ---> [  STARTED  ]     |
   |     [===========]     |
   |           |           |
 Focus       Blur      Preload
   |           |           |
   |           V           |
    ---- [===========]     |
    ---> [  BLURRED  ]     |
   |     [===========]     |
   |           |           |
 Reveal     Conceal        |
   |           |           |
   |           V           |
   |     [===========]     |
    ---- [ CONCEALED ] <---
    ---> [===========]
   |           |
Unfreeze     Freeze
   |           |
   |           V
   |     [===========]
    ---- [  FROZEN   ]
         [===========]
               |
              Stop
               |
               V
         [===========]
         [  STOPPED  ]
         [===========]

The first event that a Starboard application receives is either Start (kSbEventTypeStart) or Preload (kSbEventTypePreload). Start puts the application in the STARTED state, whereas Preload puts the application in the CONCEALED state.

In the STARTED state, the application is in the foreground and can expect to do all of the normal things it might want to do. Once in the STARTED state, it may receive a Blur event, putting the application into the BLURRED state.

In the BLURRED state, the application is still visible, but has lost focus, or it is partially obscured by a modal dialog, or it is on its way to being shut down. The application should blur activity in this state. In this state, it can receive Focus to be brought back to the foreground state (STARTED), or Conceal to be pushed to the CONCEALED state.

In the CONCEALED state, the application should behave as it should for an invisible program that can still run, and that can optionally access the network and playback audio, albeit potentially will have less CPU and memory available. The application may get switched from CONCEALED to FROZEN at any time, when the platform decides to do so.

In the FROZEN state, the application is not visible. It should immediately release all graphics and video resources, and shut down all background activity (timers, rendering, etc). Additionally, the application should flush storage to ensure that if the application is killed, the storage will be up-to-date. The application may be killed at this point, but will ideally receive a Stop event for a more graceful shutdown.

Note that the application is always expected to transition through BLURRED, CONCEALED to FROZEN before receiving Stop or being killed.

Enums

SbEventType

An enumeration of all possible event types dispatched directly by the system. Each event is accompanied by a void* data argument, and each event must define the type of the value pointed to by that data argument, if any.

Values

kSbEventTypePreload

The system may send kSbEventTypePreload in UNSTARTED if it wants to push the app into a lower resource consumption state. Applications will also call SbSystemRequestConceal() when they request this. The only events that should be dispatched after a Preload event are Reveal or Freeze. No data argument.
kSbEventTypeStart

The first event that an application receives on startup when starting normally. Applications should perform initialization, start running, and prepare to react to subsequent events. Applications that wish to run and then exit must call SbSystemRequestStop() to terminate. This event will only be sent once for a given process launch. SbEventStartData is passed as the data argument.
kSbEventTypeBlur

A dialog will be raised or the application will otherwise be put into a background-but-visible or partially-obscured state (BLURRED). Graphics and video resources will still be available, but the application could pause foreground activity like animations and video playback. Can only be received after a Start event. The only events that should be dispatched after a Blur event are Focus or Conceal. No data argument.
kSbEventTypeFocus

The application is returning to the foreground (STARTED) after having been put in the BLURRED (e.g. partially-obscured) state. The application should resume foreground activity like animations and video playback. Can only be received after a Blur or Reveal event. No data argument.
kSbEventTypeConceal

The operating system will put the application into the Concealed state after this event is handled. The application is expected to be made invisible, but background tasks can still be running, such as audio playback, or updating of recommendations. Can only be received after a Blur or Reveal event. The only events that should be dispatched after a Conceal event are Freeze or Reveal. On some platforms, the process may also be killed after Conceal without a Freeze event.
kSbEventTypeReveal

The operating system will restore the application to the BLURRED state from the CONCEALED state. This is the first event the application will receive coming out of CONCEALED, and it can be received after a Conceal or Unfreeze event. The application will now be in the BLURRED state. No data argument.
kSbEventTypeFreeze

The operating system will put the application into the Frozen state after this event is handled. The application is expected to stop periodic background work, release ALL graphics and video resources, and flush any pending SbStorage writes. Some platforms will terminate the application if work is done or resources are retained after freezing. Can be received after a Conceal or Unfreeze event. The only events that should be dispatched after a Freeze event are Unfreeze or Stop. On some platforms, the process may also be killed after Freeze without a Stop event. No data argument.
kSbEventTypeUnfreeze

The operating system has restored the application to the CONCEALED state from the FROZEN state. This is the first event the application will receive coming out of FROZEN, and it will only be received after a Freeze event. The application will now be in the CONCEALED state. NO data argument.
kSbEventTypeStop

The operating system will shut the application down entirely after this event is handled. Can only be received after a Freeze event, in the FROZEN state. No data argument.
kSbEventTypeInput

A user input event, including keyboard, mouse, gesture, or something else. SbInputData (from input.h) is passed as the data argument.
kSbEventTypeUser

A user change event, which means a new user signed-in or signed-out, or the current user changed. No data argument.
kSbEventTypeLink

A navigational link has come from the system, and the application should consider handling it by navigating to the corresponding application location. The data argument is an application-specific, null-terminated string.
kSbEventTypeVerticalSync

The beginning of a vertical sync has been detected. This event is very timing-sensitive, so as little work as possible should be done on the main thread if the application wants to receive this event in a timely manner. No data argument.
kSbEventTypeScheduled

An event type reserved for scheduled callbacks. It will only be sent in response to an application call to SbEventSchedule(), and it will call the callback directly, so SbEventHandle should never receive this event directly. The data type is an internally-defined structure.
kSbEventTypeAccessibilitySettingsChanged

The platform's accessibility settings have changed. The application should query the accessibility settings using the appropriate APIs to get the new settings. Note this excludes captions settings changes, which causes kSbEventTypeAccessibilityCaptionSettingsChanged to fire. If the starboard version has kSbEventTypeAccessib(i)lityTextToSpeechSettingsChanged, then that event should be used to signal text-to-speech settings changes instead; platforms using older starboard versions should use kSbEventTypeAccessib(i)litySettingsChanged for text-to-speech settings changes.
kSbEventTypeLowMemory

An optional event that platforms may send to indicate that the application may soon be terminated (or crash) due to low memory availability. The application may respond by reducing memory consumption by running a Garbage Collection, flushing caches, or something similar. There is no requirement to respond to or handle this event, it is only advisory.
kSbEventTypeWindowSizeChanged

The size or position of a SbWindow has changed. The data is SbEventWindowSizeChangedData .
kSbEventTypeOnScreenKeyboardShown

The platform has shown the on screen keyboard. This event is triggered by the system or by the application's OnScreenKeyboard show method. The event has int data representing a ticket. The ticket is used by the application to mark individual calls to the show method as successfully completed. Events triggered by the application have tickets passed in via SbWindowShowOnScreenKeyboard. System-triggered events have ticket value kSbEventOnScreenKeyboardInvalidTicket.
kSbEventTypeOnScreenKeyboardHidden

The platform has hidden the on screen keyboard. This event is triggered by the system or by the application's OnScreenKeyboard hide method. The event has int data representing a ticket. The ticket is used by the application to mark individual calls to the hide method as successfully completed. Events triggered by the application have tickets passed in via SbWindowHideOnScreenKeyboard. System-triggered events have ticket value kSbEventOnScreenKeyboardInvalidTicket.
kSbEventTypeOnScreenKeyboardFocused

The platform has focused the on screen keyboard. This event is triggered by the system or by the application's OnScreenKeyboard focus method. The event has int data representing a ticket. The ticket is used by the application to mark individual calls to the focus method as successfully completed. Events triggered by the application have tickets passed in via SbWindowFocusOnScreenKeyboard. System-triggered events have ticket value kSbEventOnScreenKeyboardInvalidTicket.
kSbEventTypeOnScreenKeyboardBlurred

The platform has blurred the on screen keyboard. This event is triggered by the system or by the application's OnScreenKeyboard blur method. The event has int data representing a ticket. The ticket is used by the application to mark individual calls to the blur method as successfully completed. Events triggered by the application have tickets passed in via SbWindowBlurOnScreenKeyboard. System-triggered events have ticket value kSbEventOnScreenKeyboardInvalidTicket.
kSbEventTypeReserved1

Reserved for deprecated events.
kSbEventTypeAccessibilityCaptionSettingsChanged

One or more of the fields returned by SbAccessibilityGetCaptionSettings has changed.
kSbEventTypeAccessibilityTextToSpeechSettingsChanged

The platform's text-to-speech settings have changed.
kSbEventTypeOsNetworkDisconnected

The platform has detected a network disconnection. There are likely to be cases where the platform cannot detect the disconnection but the platform should make a best effort to send an event of this type when the network disconnects. This event is used to implement window.onoffline DOM event.
kSbEventTypeOsNetworkConnected

The platform has detected a network connection. There are likely to be cases where the platform cannot detect the connection but the platform should make a best effort to send an event of this type when the device is just connected to the internet. This event is used to implement window.ononline DOM event.
kSbEventDateTimeConfigurationChanged

The platform has detected a date and/or time configuration change (such as a change in the timezone setting). This should trigger the application to re- query the relevant APIs to update the date and time.

Typedefs

SbEventCallback

A function that can be called back from the main Starboard event pump.

Definition

typedef void(* SbEventCallback) (void *context)

SbEventDataDestructor

A function that will cleanly destroy an event data instance of a specific type.

Definition

typedef void(* SbEventDataDestructor) (void *data)

SbEventId

An ID that can be used to refer to a scheduled event.

Definition

typedef uint32_t SbEventId

Structs

SbEvent

Structure representing a Starboard event and its data.

Members

SbEventType type
int64_t timestamp
void * data

SbEventStartData

Event data for kSbEventTypeStart events.

Members

char ** argument_values

The command-line argument values (argv).
int argument_count

The command-line argument count (argc).
const char * link

The startup link, if any.

SbEventWindowSizeChangedData

Event data for kSbEventTypeWindowSizeChanged events.

Members

SbWindow window
SbWindowSize size

Functions

SbEventCancel

Cancels the specified event_id. Note that this function is a no-op if the event already fired. This function can be safely called from any thread, but the only way to guarantee that the event does not run anyway is to call it from the main Starboard event loop thread.

Declaration

void SbEventCancel(SbEventId event_id)

SbEventHandle

The entry point that Starboard applications MUST implement. Any memory pointed at by event or the data field inside event is owned by the system, and that memory is reclaimed after this function returns, so the implementation must copy this data to extend its life. This behavior should also be assumed of all fields within the data object, unless otherwise explicitly specified.

This function is only called from the main Starboard thread. There is no specification about what other work might happen on this thread, so the application should generally do as little work as possible on this thread, and just dispatch it over to another thread.

Declaration

SB_EXPORT_PLATFORM void SbEventHandle(const SbEvent *event)

SbEventIsIdValid

Returns whether the given event handle is valid.

Declaration

static bool SbEventIsIdValid(SbEventId handle)

SbEventSchedule

Schedules an event callback into the main Starboard event loop. This function may be called from any thread, but callback is always called from the main Starboard thread, queued with other pending events.

callback: The callback function to be called. Must not be NULL. context: The context that is passed to the callback function. delay: The minimum number of microseconds to wait before calling the callback function. Set delay to 0 to call the callback as soon as possible.

Declaration

SbEventId SbEventSchedule(SbEventCallback callback, void *context, int64_t delay)

SbRunStarboardMain

Serves as the entry point in the Starboard library for running the Starboard event loop with the application event handler.

Declaration

int SbRunStarboardMain(int argc, char **argv, SbEventHandleCallback callback)